Corrosion-inhibiting composition of mixture of molasses, potassium iodide and metal salt of a fatty acid



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UUnitedfStates P311 This application is a continuation of our priorapplication SN. 854,221, filed November 20, 1959, now abandohed.

This invention relates to novel corrosion inhibiting compositions. Thisinvention also relates to a method of inhibiting the corrosion effect ofaqueous solutions of strong inorganic acidic compounds on mild steel.

Theterm mild steel as used throughout the descrip tion and claims isintended to include plain carbon steels designated by the Society ofAutomotive Engineers as the. 171000 "series, having an SAE numberbetween about 10-110 and 1095, but other steels having limitedcorrosionresisting powers are also included;

Corrosion of mild steel by concentrated aqueous solutions of strongacidic compounds has long been a prob- 1cm in. the chemical industry.Because of these corrosive properties, ithas been necessary to employequipment constructed of. expensive. corrosion-resisting materials inPIOCCSSESIWhGTfi concentrated aqueous solutions of stronginorganicacidic compounds are employed.

Solid dicalcium phosphate has been used for many years by the animalfeed industry as a source of phosphorus for animalfeeds. Dicalciumphosphate can be admixed with other: animal feed ingredients in mixers,pug mills, pelletizers and other processing equipment constructed ofmild steel with little or no corrosive effect thereon. Concentratedphosphoric acid has more recently been employed as a source ofphosphorus for animal feeds. When compareclw-ithdicalcium phosphate,phosphoric acid is easier toliandle and is easier to mix with otheranimal feed ingredients; 11 In addition, animal feeds containingphosphoric acid are generally more palatable to ruminants than animalfeedsipreparedfrom dicalciu m phosphate. However, one seriousdisadvantage in the use of concentrated phosphoricacid as a component ofanimal feeds is that the acid is extremely corrosive to mild steel, theconstruction material normally employed in the animal feed industry.

-As a result, the many advantages in the use of phosphoric acid as acomponent of animal feeds are over-shadowed by the expense involved incoating the original mild steel equipment to prevent corrosion by theacid and/or the purchase of new equipment constructed ofcorrosion-resisting materials.

It is a primary object of this invention to provide novel corrosioninhibitors.

It I is a further object of the. invention to provide a method ofinhibiting the corrosive effect of aqueous solu- "ice These and otherobjects of the invention will be apparent from the following detaileddescription.

It has now been discovered that aqueous solutions of strong inorganicacidic compounds can be rendered substantially non-corrosive to mildsteel when a corrosioninhibiting proportion of a mixture of molasses andpotassium iodide is dispersed in the acid. If either molasses orpotassium iodide is added to an acid such as phosphoric acid, and thetreated acids are placed in agitated contact with mild steel, either ofthe treated acids is less corrosive than untreated phosphoric acid underthe same conditions. However, it has been discovered that if bothmolasses and potassium iodide are admixed with concentrated phosphoricacid, preferably in the presence of a stabilizer, and the treated acidis placed in agitated contact with mild steel, there is a synergisticeffect attained, and the acid thus treated is substantiallynon-corrosive to the mild steel.

More in detail, any aqueous solution of a strong inorganic acidiccompound which corrodes mild steel when in agitated contact therewith,can be treated in accordance with the technique of the instantinvention. Typical strong inorganic acidic compounds includeorthophosphoric acid, metaphosphoric acid, pyrophospho-ric acid,monocalcium phosphate, hypophosphorous acid, hydrochloric acid, sulfuricacid and mixtures thereof.

Any concentration of the acidic inorganic compound in the aqueoussolution that has a corrosive effect upon mild steel can be treated inaccordance with the technique of the instant invention. For example,orthophosphoric acid solutions having an H PO concentration up to aboutone hundred percent, and preferably between about twenty and aboutninety percent by weight can be effectively treated to inhibitcorrosion. Sulfuric acid solutions having an H So concentration up toabout eighty percent by weight, can also be effectively treated.

Blackstrap molasses is preferably employed as a component of thecor-rosion inhibiting mixture, but any molasses, such as corn molasses,beet molasses, citrus molasses, wood molasses, or mixtures thereof maybe employed. Molasses is used in its usual commercial form, whichcontains between about fifteen and about fifty percent water by weight.Molasses is admixed with the aqueous solution of strong acidic inorganiccompound in a proportion equivalent to between about three and aboutfifty, and preferably between about eight and about twenty parts ofmolasses (dry basis) per two thousand parts of acidic inorganic compound(dry basis) in the aqueous solution. If a weight ratio of molasses toacidic compound of less than about 322000 is employed, corrosion is noteffectively inhibited. If a weight ratio of greater than about 5012000is employed, corrosion is effectively inhibited, but the acid solutionmay be unnecessarily adulterated with molasses.

Potassium iodide is admixed with the aqueous acidic solution in aproportion equivalent to between about 0.2 and about twenty, andpreferably between about 0.2 and about 0.5 part of KI per two thousandparts of acidic in organic compound in the aqueous solution. If a weightratio of less than about 0.2 part per two thousand parts is employed.corrosion of the mild steel is not effectively inhibited. On the otherhand, a weight ratio greater than about twenty parts KI per two thousandparts of acidic compound is employed, corrosion is effectivelyinhibited, but the acid solution may be unnecessarily adulterated withKI.

The weight ratio of molasses to potassium iodide is preferably betweenabout 25 :1 and about :1.

It is preferred to add a small but effective proportion of a stabilizerto the acidic solution in order to enhance the effectiveness of thepotassium iodide component of the corrosion-inhibiting mixture. Fattyacid salts of metals in the alkali metal group, alkaline earth metalgroup and earth metal group of the periodic table can be employed as astabilizer. Typical examples of suitable stabilizers include calciumstearate, calcium oleate, calcium pahnitate, the corresponding aluminumsalts, the corresponding sodium salts and mixtures thereof.

The stabilizer is preferably admixed with the acid solution in aproportion equivalent to a weight ratio of potassium iodide tostabilizer of between about 5:1 and about 15:1, but smaller or greaterproportions may be employed if desired.

The aqueous solution of the strong inorganic acidic compound, molassesand potassium iodide, with or without a stabilizer, are admixed in theabove described proportions in a suitable container provided withagitation means. It is preferred to add the ingredients simultaneouslyto the container, but the order of mixing the ingredients is notcritical so long as a substantially homogeneous mixture is attained. Ifdesired, molasses, potassium iodide, with or without a stabilizer arepremixed in the above defined proportions prior to adding to the acidicsolution.

Mixing of the ingredients is preferably carried out at room temperature,but higher or lower temperatures may be employed if desired.

Concentrated aqueous solutions of a strong inorganic acidic compoundwhich have been treated in accordance with the novel technique of thisinvention may be stored and/or agitated in mild steel containers orother equipment without causing significant corrosion of the mild steel.The novel technique is particularly suitable for treating concentratedphosphoric acid used in the preparation of animal feeds and animal feedsupplements, since the corrosion inhibiting ingredients are not toxic toanimals. For example, concentrated phosphoric acid treated with theaforesaid corrosion inhibiting ingredients may be admixed with molasses,urea, and water to prepare a feed supplement for ruminants in accordancewith the technique set forth in United States Patent No. 2,748,001,

resin was employed. An SAE 1010 mild carbon steel probe, three inches byone-eighth of an inch, was secured in each beaker, positioned normal tothe path of agitation, the radius from the center of rotation to thecenter of the probe being about three inches. The thickness of theprobes are indicated below in the table. About four liters of phosphoricacid, containing about eighty percent H PO by weight, produced by thefurnace method was added to each beaker. The acid portions before andafter adding reagents were agitated at the rate of about two hundredrevolutions per minute. After five hours of exposure under theseconditions, the following reagents were admixed with the phosphoric acidin the following proportions:

Example 1: one gallon black strap molasses per ton of eighty percentacid. Example 2: four ounces potassium iodide per ton of eighty percentacid. Example 3:

One gallon black strap molasses per ton of eighty percent acid. Fourounces potassium iodide per ton of eighty percent acid. Example 4:

One gallon black strap molasses per ton of eighty percent acid. Fourounces C.P. potassium iodide per ton of eighty percent acid. 0.4 ouncecalcium stearate per ton of eighty percent acid.

After thirty-four hours of exposure, air was bubbled into each agitatedsolution at the rate of about 0.7 liter per minute. The air was turnedoff at the end of fiftythree hours in Example 3, and after aboutfifty-five hours in Examples 1, 2 and 4. Corrosion of the mild steelprobes was determined periodically with a Labline Corrosion meter. Thefollowing table sets forth the results obtained in each test.

CORROSION PENETRATION, JMICROINCHES mil probe) (10 mil probe) (10 milprobe) (10 mil probe) Exposure Time, Example 1 Example 2 Example 3Example 4 Hours Acid and Molasses Acid and KI Acid-l-Molasses-l-KIAcid+Molasses+ KI and Ca Stearate O. 5 10. 0 9.0 5.0 5. 0 5. 0 376. 0385. 0 282. 0 338. 0 Reagents added at end of fifth hour 6. 0 404. 0415. 0 300. O 347. 0 84. 0 654. 0 565. 0 460. 0 370.

Ai added at end of 34th hour 35.0 666. 0 590. 0 460.0 370.0 53. 0 882. 0842. 0 478. 0 397. 0

(Air oil) 54. 0 836. 0 898.0 478. 0 403. 0 55.0 860.0 927. 0 478. 0 403.0 (Air oft) (Air ofi) (Air 011?) 119.0 1, 184 On Scale 478. 406. 0 127.O 1, 270 1, 000) 495. 0 406. 0

Examples 14 The effect of four concentrated aqueous phosphoric acidsolutions, containing various additives, on the corrosion of mild steelwas determined in accordane with the following procedure. The four acidsolutions were designated as Examples 1, 2, 3 and 4 respectively. Ineach example, a four liter glass beaker provided with a motor drivenpaddle coated with a tetrafluoroethylene It can be seen from the abovetable that neither molasses alone (Example 1) nor potassium iodide alone(Example 2) effectively inhibited corrosion of the mild steel probes,while the novel inhibitors of Examples 3 and 4 markedly inhibitcorrosion of the mild steel probes.

Examples 5-6 The procedure of Examples 2-4 was repeated with thefollowing exceptions. The corrosion inhibiting compounds were added tothe phosphoric acid at the start of the tests, and air was not bubbledthrough the solutions during the tests. The following inhibitors andproportions were employed.

Example 5:

Four ounces potassium iodide per ton of eighty percent acid. 0.4 ouncesodium oleate per ton of eighty percent acid.

Example 6:

Four ounces potassium iodide per ton of eighty percent acid. 0.4 ouncealuminum stearate per ton of eighty percent acid.

The following table sets forth the results obtained in each test.

CORROSION PENETRATION,

ltiican be seen from these tests that sodium oleate and aluminumstearate effectively stabilize the corrosion inhibiting properties of KIfor at least about fifty-seven hours.

Example 7 An. aqueous fifty percent sulfuric acid solution was tested inaccordance with the procedure of Examples 5 and 6, employing thefollowing inhibitors and proportions:

One gallonblack strap. molasses per ton of fifty percent acid.:

Four ounces potassium iodide per ton of fifty percent acid.

0.4 ouncecalcium stearate per. ton of fifty percent acid.

The. following table sets forth the results obtained in this test.

Exposure time, Corrosion penetration,

hours microinches 2.5 50 21.25 110 77.5 110 119.0 112 126.0 149 145.0 1186 217.0 186 It; will be recognized by those skilled in the art thatWhat is claimed is:

1. A corrosion-inhibiting composition for aqueous solutions of strongacidic inorganic compounds selected from the group consisting ofphosphoric acid, monocalcium phosphate, hypophosphorus acid,hydrochloric acid, sulfuric acid and mixtures thereof, which compositionconsists essentially of a mixture of molasses, potassium iodide and ametal salt of a fatty acid, the weight ratio of molasses to potassiumiodide in said mixture being between about 25:1 and about 100:1, and theweight ratio of potassium iodide to said metal salt being between about5:1 and about 15:1, said metal salt of a fatty acid being a salt of ametal selected from the group consisting of calcium, sodium, andaluminum, and a fatty acid selected from the group consisting of oleic,stearic,

W and palmitic acid.

variousi. modifications within the invention are possible,

some of which have been referred to above. Therefore,

we do. not wish to be limited except as defined by the appended claims.

2. The composition of claim 1 wherein said metal salt is calciumstearate.

3. A corrosion-resisting composition consisting essentially of anaqueous solution of a strong acidic inorganic compound selected from thegroup consisting of phosphoric acid, mono-calcium phosphate,hypophosphorus acid, hydrochloric acid, sulfuric acid and mixturesthereof, containing molasses in a proportion between about three andabout fifty parts of molasses, dry basis, per two thousand parts of saidacidic compound, potassium iodide in a proportion between about 0.2 andabout twenty parts potassium iodide per two thousand parts of saidacidic compound, and a metal salt of a fatty acid in the proportion ofone part of said metal salt to between about five and about fifteenparts of said potassium iodide, said metal salt of a fatty acid being asalt of a metal selected from the group consisting of calcium, sodiumand aluminum and a fatty acid selected from the group consisting ofoleic, stearic, and palrnitic acid.

4. The composition of claim 3 wherein said acidic compound is phosphoricacid.

5. The composition of claim 3 wherein said acidic compound is sulfuricacid.

6. The composition of claim 3 wherein said metal salt is calciumstearate.

References Cited by the Examiner UNITED STATES PATENTS 1,809,041 6/1931Jenkins et al. 252-136 1,935,911 11/1933 Neilson 252-136 1,948,0292/1934 Fisher 252-396 2,382,193 8/1945 Whitmoyer et al. 99-2 2,708,1845/1955 Hager et al. 252-147 3,062,612 11/1962 Boucher 252-146 FOREIGNPATENTS 569,138 5/ 1945 Great Britain.

SAMUEL H. BLECH, Primary Examiner.

JULIUS GREENWALD, ALBERT T. MEYERS,

Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 296,149 January 3, 1967 Errol P, Cook et a1,

It is hereby certified that error appears in the above numbered pat entrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 71, for accordane" read accordance columns 3 and 4, inthe table, second column, line 6 thereof, for "882 o 0" read 822 a 0 nSigned and sealed this 28th day of November 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr.

EDWARD J. BRENNER

1. A CORROSION-INHIBITING COMPOSITION FOR AQUEOUS SOLUTIONS OF STRONGACIDIC INORGANIC COMPOUNDS SELECTED FROM THE GROUP CONSISTING OFPHOSPHORIC ACID, MONOCALCIUM PHOSPHATE, HYPHOPHOSPHORUS ACID,HYDROCHLORIC ACID, SULFURIC ACID AND MIXTURES THEREOF, WHICH COMPOSITIONCONSISTS ESSENTIALLY OF A MIXTURE OF MOLASSES, POTASSIUM IODIDE AND AMETAL SALT OF A FATTY ACID, THE WEIGHT RATIO OF MOLASSES TO POTASSIUMIODIDE IN SAID MIXTURE BEING BETWEEN ABOUT 25:1 AND ABOUT 100:1, AND THEWEIGHT RATIO OF POTASSIUM IODIDE TO SAID METAL SALT BEING BETWEEN ABOUT5:1 AND ABOUT 15:1, SAID METAL SALT OF A FATTY ACID BEING A SALT OF AMETAL SELECTED FROM THE GROUP CONSISTING OF CALCIUM, SODIUM, ANDALUMINUM, AND A FATTY ACID SELECTED FROM THE GROUP CONSISTING OF OLEIC,STEARIC, AND PALMITIC ACID.